The soil microbe Bacillus thuringiensis (B.t.) is a Gram-positive, spore-forming bacterium characterized by parasporal crystalline protein inclusions. These inclusions often appear microscopically as distinctively shaped crystals. The proteins can be highly toxic to pests and specific in their toxic activity. Certain B.t. toxin genes have been isolated and sequenced, and recombinant DNA-based B.t. products have been produced and approved for use. In addition, with the use of genetic engineering techniques, new approaches for delivering these B.t. endotoxins to agricultural environments are under development, including the use of plants genetically engineered with endotoxin genes for insect resistance and the use of stabilized intact microbial cells as B.t. endotoxin delivery vehicles (Gaertner, F. H., L. Kim [1988] TIBTECH 6:S4-S7). Thus, isolated B.t. endotoxin genes are becoming commercially valuable.
Until the last ten years, commercial use of B.t. pesticides has been largely restricted to a narrow range of lepidopteran (caterpillar) pests. Preparations of the spores and crystals of B. thuringiensis subsp. kurstaki have been used for many years as commercial insecticides for lepidopteran pests. For example, B. thuringiensis var. kurstaki HD-1 produces a crystalline xcex4-endotoxin which is toxic to the larvae of a number of lepidopteran insects.
In recent years, however, investigators have discovered B.t. pesticides with specificities for a much broader range of pests. For example, other species of B.t., namely israelensis and tenebrionis (a.k.a. B.t. M-7, a.k.a. B.t. san diego), have been used commercially to control insects of the orders Diptera and Coleoptera, respectively (Gaertner, F. H. [1989] xe2x80x9cCellular Delivery Systems for Insecticidal Proteins: Living and Non-Living Microorganisms,xe2x80x9d in Controlled Delivery of Crop Protection Agents, R. M. Wilkins, ed., Taylor and Francis, New York and London, 1990, pp. 245-255). See also Couch, T. L. (1980) xe2x80x9cMosquito Pathogenicity of Bacillus thuringiensis var. israelensis,xe2x80x9d Developments in Industrial Microbiology 22:61-76; Beegle, C. C., (1978) xe2x80x9cUse of Entomogenous Bacteria in Agroecosystems,xe2x80x9d Developments in Industrial Microbiology 20:97-104. Krieg, A., A. M. Huger, G. A. Langenbruch, W. Schnetter (1983) Z. ang. Ent. 96:500-508, describe Bacillus thuringiensis var. tenebrionis, which is reportedly active against two beetles in the order Coleoptera. These are the Colorado potato beetle, Leptinotarsa decemlineata, and Agelastica alni. 
Recently, new subspecies of B.t. have been identified, and genes responsible for active xcex4-endotoxin proteins have been isolated (Hxc3x6fte, H., H. R. Whiteley [1989] Microbiological Reviews 52(2):242-255). Hxc3x6fte and Whiteley classified B.t. crystal protein genes into 4 major classes. The classes were CryI (Lepidoptera-specific), CryII (Lepidoptera- and Diptera-specific), CryIII (Coleoptera-specific), and CryIV (Diptera-specific). The discovery of strains specifically toxic to other pests has been reported. (Feitelson, J. S., J. Payne, L. Kim [1992] Bio/Technology 10:271-275).
The cloning and expression of a B.t. crystal protein gene in Escherichia coli has been described in the published literature (Schnepf, H. E., H. R. Whiteley [1981] Proc. Natl. Acad. Sci. USA 78:2893-2897). U.S. Pat. No. 4,448,885 and U.S. Pat. No. 4,467,036 both disclose the expression of B.t. crystal protein in E. coli. U.S. Pat. Nos. 4,797,276 and 4,853,331 disclose B. thuringiensis strain tenebrionis (a.k.a. M-7, a.k.a. B.t. san diego) which can be used to control coleopteran pests in various environments. U.S. Pat. No. 4,918,006 discloses B.t. toxins having activity against Dipterans. U.S. Pat. No. 4,849,217 discloses B.t. isolates which have activity against the alfalfa weevil. U.S. Pat. No. 5,208,077 discloses coleopteran-active Bacillus thuringiensis isolates. U.S. Pat. No. 5,151,363 and U.S. Pat. No. 4,948,734 disclose certain isolates of B.t. which have activity against nematodes. As a result of extensive research and investment of resources, other patents have issued for new B.t. isolates and new uses of B.t. isolates. However, the discovery of new B.t. isolates and new uses of known B.t. isolates remains an empirical, unpredictable art.
Coleopterans are an important group of agricultural pests which cause a very large amount of damage each year. Examples of coleopteran pests include alfalfa weevils and corn rootworm.
The alfalfa weevil, Hypera postica, and the closely related Egyptian alfalfa weevil, Hypera brunneipennis, are the most important insect pests of alfalfa grown in the United States, with 2.9 million acres infested in 1984. An annual sum of 20 million dollars is spent to control these pests. The Egyptian alfalfa weevil is the predominant species in the southwestern U.S., where it undergoes aestivation (i.e., hibernation) during the hot summer months. In all other respects, it is identical to the alfalfa weevil, which predominates throughout the rest of the U.S.
The larval stage is the most damaging in the weevil life cycle. By feeding at the alfalfa plant""s growing tips, the larvae cause skeletonization of leaves, stunting, reduced plant growth, and, ultimately, reductions in yield. Severe infestations can ruin an entire cutting of hay. The adults, also foliar feeders, cause additional, but less significant, damage.
Approximately 9.3 million acres of U.S. corn are infested with corn rootworm species complex each year. The corn rootworm species complex includes the northern corn rootworm; Diabrotica barberi, the southern corn rootworm, D. undecimpunctata howardi, and the western corn rootworm, D. virgifera virgifera. The soil-dwelling larvae of these Diabrotica species feed on the root of the corn plant, causing lodging. Lodging eventually reduces corn yield and often results in death of the plant. By feeding on cornsilks, the adult beetles reduce pollination and, therefore, detrimentally effect the yield of corn per plant. In addition, adults and larvae of the genus Diabrotica attack cucurbit crops (cucumbers, melons, squash, etc.) and many vegetable and field crops in commercial production as well as those being grown in home gardens.
Control of corn rootworm has been partially addressed by cultivation methods, such as crop rotation and the application of high nitrogen levels to stimulate the growth of an adventitious root system. However, chemical insecticides are relied upon most heavily to guarantee the desired level of control. Insecticides are either banded onto or incorporated into the soil. The major problem associated with the use of chemical insecticides is the development of resistance among the treated insect populations.
The subject invention concerns novel materials and methods for controlling non-mammalian pests. In a preferred embodiment, the subject invention provides materials and methods for the control of coleopteran pests. In specific embodiments, the materials and methods described herein are used to control alfalfa weevil and/or corn rootworm.
The subject invention advantageously provides two new classes of polynucleotide sequences which encode corresponding novel classes of pesticidal proteins. One novel class of polynucleotide sequences as described herein encodes toxins which have a full-length molecular weight of approximately 40-50 kDa. In a specific embodiment, these toxins have a molecular weight of about 43-47 kDa. A second class of polynucleotides, which encodes pesticidal proteins of about 10-15 kDa, is also provided according to the subject invention. In a specific embodiment, these toxins have a molecular weight of about 13-14 kDa. The subject invention concerns polynucleotides which encode the 40-50 kDa and 10-15 kDa toxins, polynucleotides which encode pesticidal fragments of the full length toxins, and polynucleotide sequences which encode longer forms of these toxins which include, for example, a protoxin region. In a preferred embodiment, these toxins, including the fragments, are active against coleopteran pests.
Specific B.t. toxins useful according to the invention include toxins which can be obtained from the B.t. isolates designated as PS80JJ1, PS149B1, and PS167H2. Of these, PS149B1 and PS167H2 are novel isolates. The subject invention also includes the use of variants of the exemplified B.t. isolates and toxins which have substantially the same coleopteran-active properties as the specifically exemplified B.t. isolates and toxins. Such variant isolates would include, for example, mutants. Procedures for making mutants are well known in the microbiological art. Ultraviolet light and chemical mutagens such as nitrosoguanidine are used extensively toward this end.
In one embodiment of the subject invention, the polynucleotide sequences of the subject invention are used to encode toxins of approximately 43-47 kDa. These toxins are then used to control coleopteran pests. In a particularly preferred embodiment, the coleopteran pests are corn rootworms. The genes which encode the 43-47 kDa toxins can be obtained from, for example, PS80JJ1, PS149B1, or PS167H2. In a second embodiment, toxins of approximately 13-14 kDa are used to control coleopteran pests. The approximately 13-14 kDa toxin, as well as the genes which encode these toxins, can also be obtained from PS80JJ1, PS149B1, or PS167H2. In a particularly preferred embodiment, the activity of the 43-47 kDa toxins can be augmented and/or facilitated by further contacting the target pests with an approximately 13-14 kDa toxin.
In a preferred embodiment, the subject invention concerns plants cells transformed with at least one polynucleotide sequence of the subject invention such that the transformed plant cells express pesticidal toxins in tissues consumed by the target pests.
Alternatively, the B.t. isolates of the subject invention, or recombinant microbes expressing the toxins described herein, can be used to control pests. In this regard, the invention includes the treatment of substantially intact B.t. cells, and/or recombinant cells containing the expressed toxins of the invention, treated to prolong the pesticidal activity when the substantially intact cells are applied to the environment of a target pest. The treated cell acts as a protective coating for the pesticidal toxin. The toxin becomes active upon ingestion by a target insect.